Graphene lenses for electrons

April 23, 2012

Graphen lens (credit: Karlsruhe Institute of Technology)

Graphene, the one-atom-thick “wonder material” made of carbon, has another potential use in the world of high-speed electronics — as a tool that can focus a stream of electrons similar to the way an optical lens focuses light.

Graphene is an excellent conductor: electrons flow freely across its surface in straight lines. According to a previously proposed theory, highly strained graphene impedes the flow of electrons, slowing them down and altering their trajectory. Scientists believed this effect could be used to focus electrons to a fine point — similar to the way an optical lens creates areas of refraction, or bending, to shepherd light to a point.

To create the prototype lens, the team of French and German researchers built a “deformed graphene carpet” that smoothly covers a series of hexagonal nano-holes in a silicon-carbide wafer. Areas of the graphene were strained as they adopted the shape of the holes in the wafer. The researchers found that they could control the focal length of a graphene lens by changing its geometry.

Practical applications of this work include uses in high-speed electronics, where strained graphene could act as a transport medium for information exchange between different parts of a circuit. Unlike traditional information exchange, in which electrons flow through cables whose paths cannot cross without a short, the new method would allow electrons an unprecedented freedom of movement, similar to that of light in a vacuum.

“The advantage of this method can be seen if you have n contacts, between those you would like to send information. With cables, you need for every connection one cable (that make n(n-1)/2 cables). In the new way, you can use lenses to focus electrons from one contact to another contact. Thus, you only need one two-dimensional graphene layer for the information transport and all the n(n-1)/2 paths of the electrons can just cross each other in the layer,” adds Karlsruhe Institute of Technology’s Dr. W. Wulfhekel.